Finding large DBs for researchs

I've looked quite a lot on the net, for a large DB (10000xRows as a minimum, and 20 columns), which contains data which I could work on.

I'm working now on my Msc thesis in IT.

In my work I'm testing prediction of cases. I'm running several Neural Networks on DB's.

Where can I find such DB's? When I say DB's I mean DB's with historical data on a human (e.g. ?health history, with deseases - I'm...